This invention relates to disposable hypodermic syringes, fitted with a sliding telescopic protector and characterized by a unique control and locking system therefor.
In 1989, with the spread of AIDS, the grave potential of increased risk of accidental puncture to medical and paramedical personnel was recognized. It has been reported that another aspect of AIDS constitutes vulnerability due to contamination of the health equipment involved in direct patient assistance, and it is accepted that using a double pair of gloves, mask and apron, avoiding direct contact with blood or discharge, does not diminish accidents with needles. It is reported that punctures with injectable materials constitutes 80% of the medical accidents and not only transmits the AIDS virus but also Hepatitis B virus which causes the most serious forms of that illness. A very high percentage of punctures could be avoided by the utilization of syringes with some protective mechanism. Of all the problems posed by AIDS, this is presently the only one which could have a 90% resolution. It is therefore an object of this invention to solve the problem by achieving a most economically viable and practical solution that maximizes safety.
Of the many ways in which this matter has been dealt, the most common among them is the adoption of a telescopic hood or shield which, when the syringe has been used, slides forward to cover the needle. It is therefore an object of this invention to provide a system characterized by a lock designed to affix the hood in a protective position covering the needle.
Searching logically for a disposable product of the least possible cost gave imeptus, principally in the United States, to inumerable patents, but none of them have reached a stage of mass production. The reason for this is obvious: to attain a non-conventional complex syringe design that requires special materials invariably exceeds pruduction costs which the market cannot accept.
Specifically, U.S. Pat. No. 4,738,663 to shows a hypodermic meedle protector made up of a telescopic tube with both ends open and secured to the syringe cylinder, which maintains a retracted or extended position (alternately), which in the second instance covers the needle. However, the previous forms of locks to keep the protector in the extended position, simple "thorns" of plastic material, could be easily removed and thus accidently expose a potentially contaminated needle.
U.S. Pat. No. 4,747,837 to Hauck shows another tubular hood. In this patent the hood includes a protruded edge of plastic material which fits when in an extended position into a furrow or a circular groove near the end of the discharged hypodermic needle. However, as the hood and edge are necessarily formed in one piece from the same material, it is difficult, industrially to reconcile the rigidity required for the first, with the plasticity required for the second. Furthermore, this system is not adaptable to existing syringes that are excluded for lack of a circular groove.
With reference to U.S. Pat. No. 4,850,994 to Zerbst a hypodermic syringe is shown in which a tubular case is alternately placed in a retracted or an extended position. However, it will be noted that retainers or catches in this case are molded on the syringe cylinder, which results in a weakening of the same. Forthermore, as in all the other prior art patents it requires special syringe manufacture.
U.S. Pat. No. 4,737,144 to Choksi also includes a sliding hood which can be placed in retracted or extended positions. In this patent the lock constitutes an appendage of the hood which fits in a round groove built on the syringe near the hypodermic needle. Similarly, U.S. Pat. No. 4,631,057 to Mitchell shows a sliding case for a hypodermic needle which can be selectively placed in an open or closed position, the lock constituting a ring which in the extended position fits into a special flange of the syringe cylinder, which obviously must be specially manufactured.
In 1991 this inventor was issued Argentina Patent No. 321,339 entitled Accessory Of Prophylaxis For Hypodermic Syringes, which partially overcame the problem here under consideration. That accessory used a sliding telescopic hood with a locking sytem which could be incorporated in any already manufactured syringe. Thus in principle, the product is commercially feasible. Nevertheless until the present time it also has not had wide distribution, since the cost of the accessory nearly duplicates that of the basic syringe, due to the need to rivet a costly non-oxidizable steel lock on each hood. On the other hand, in order to avoid reuse of the syringe or at least the easy separation from the hood, and its recoil to its original position, it necessitates an upgrade of quality in the material used, as it is fixed under pressure, and special care must be taken to the "tip" which is attached to the syringe which is sharp and generates a high degree of friction asgainst the plastic surface and must be reliably riveted, all of which raises the price of mass production.
Therefore, it has required ingenuity to reconcile the three latter suppositions which are contradictory among themselves: simplicity, effectiveness, and manufacturing tolerances.
The foregoing and various other objects and features of this invention will be apparent and fully understood from the following detailed description of the typical preferred form and application thereof, throughout which description reference is made to the the accompanying drawings.